Engine Break-In. Part 2. Test Runs.
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Proper engine Break-In will produce an engine that achieves maximum power output with the least amount of oil consumption. When the piston rings are properly broken-in, they keep combustion gases in the combustion chamber and prevent gases escaping past the piston rings into the crankcase section of the engine. This reduced "blow-by" keeps your engine running cleaner and cooler. Excessive "blow-by" increases crankcase pressure and contaminates the oil with combustion gases. Also, if the rings do not seat properly, they cannot keep excess oil off the cylinder walls. The result is an engine that consumes more than its share of oil
During the first few test runs, keep the temperatures to a minimum while providing an opportunity to check for leaks and verify the installation is airworthy. During these first few test runs, the engine RPMs and engine temps are gradually increased. These runs put very little pressure on the rings; ring break-in is not the objective. Rather, these engine runs let the cam, lifters, main and rod bearings, and all the other moving parts, get to know each other. Take your time and follow these steps.
I recommend you break-in your new engine (or cylinders) with AeroShell 15W-50. I've been doing it this way since 1991.
The engine baffles must be installed. The cowling must be installed.
Step 6: First engine run (800 RPM) . . . . . 1 minute. This is to make sure you are ready for the next step.
• Start and run the engine for one minute at 800 RPM and observe
-- oil pressure (40 to 60 psi; minimum 25 psi)
-- fuel pressure (0.5 to 8 psi, carbureted; 14 to 45 psi, fuel injected)
-- alternator output (see Pilots Operating Manual for your aircraft)
• Throttle to IDLE.
• Check IDLE RPM.
• Shut down.
Check for leaks. Allow engine to cool for 10 to 15 minutes.
Step 7: Second engine test run (1200 RPM) . . . . 15 minutes. This is to get the oil temp up and check IDLE rpm and IDLE mixture.
• Start and run engine at 1000 RPM until oil temperature reaches 100°F minimum (greater than 140°F is preferred)
• Check
-- oil pressure (40 to 60 psi; minimum 25 psi)
-- fuel pressure (0.5 to 8 psi, carbureted; 14 to 45 psi, fuel injected)
Advance throttle to 1200 RPM and observe
• Check
-- oil pressure (40 to 60 psi; minimum 25 psi)
-- fuel pressure (0.5 to 8 psi, carbureted; 14 to 45 psi, fuel injected)
• Run engine for fifteen (15) minutes.
-- Make sure the cylinder head temperatures does not exceed 420°F on a JPI EDM engine analyzer (380°F on any other analyzer)
• Reduce power to idle, observe IDLE rpm.
• Pull mixture out slowly to IDLE cutoff.
-- Observe tachometer for RPM rise.
- Carbureted engines: 25 to 50 RPM increase.
- Fuel Injected engines: 20 to 30 RPM increase.
• Inspect engine for oil and fuel leaks
• Make small adjustments to IDLE and mixture as necessary We want about 700 rpm at this point.
Note: We'll cover setting the engine IDLE rpm on a separate link.---> Setting the Engine Idle:
Check for leaks. Allow engine to cool for 10 minutes.
Step 8: Third engine test run (1800 RPM and Mag Check)
• Start engine and monitor oil pressure at or near IDLE rpm (600 rpm)
• Advance throttle to 1200 RPM for five (5) minutes.
• Check
-- oil pressure (40 to 60 psi; minimum 25 psi)
-- oil temperature greater than 140°F
-- fuel pressure (0.5 to 8 psi, carbureted; 14 to 45 psi, fuel injected)
• Advance throttle to 1800 RPM. (lean mixture to peak RPM.)
• Perform magneto check. Note the RPM change for each magneto.
-- Right Mag: ______________________
-- Left Mag: ______________________
• On aircraft with controllable pitch prop:
a. Pull prop control out for 10 seconds (maximum).
- - - Observe oil pressure.
- - - RPM drop. 100 to 300 rpm
b. Push prop control back. Observe oil pressure.
• Pull mixture out slowly to IDLE cutoff.
-- Observe tachometer for RPM rise.
- Carbureted engines: 25 to 50 RPM increase.
- Fuel Injected engines: 20 to 30 RPM increase.
• Inspect engine for oil and fuel leaks
• Make small adjustments to IDLE and mixture as necessary
Check for leaks. Allow engine to cool for 20 minutes.
Step 9: Final engine run
• Start engine and monitor oil pressure at or near IDLE rpm (600 to 700 rpm)
• Advance throttle to 1200 RPM for five (5) minutes.
• Check
-- oil pressure (40 to 60 psi; minimum 25 psi)
-- oil temperature greater than 140°F
-- fuel pressure (0.5 to 8 psi, carbureted; 14 to 45 psi, fuel injected)
• Advance throttle to 1800 RPM.
• On aircraft with controllable pitch prop:
a. Pull prop control out for 10 seconds (maximum).
- - - Observe oil pressure.
- - - RPM drop. 100 to 300 rpm
b. Push prop control back. Observe oil pressure.
• Advance throttle to full static RPM. (lean mixture to peak RPM.)
• Run engine to full static airframe recommended power for a period not to exceed 10 seconds.
-- If you have an engine monitor, keep CHTs below 425°F (JPI EDM engine analyzer)
-- Record peak static RPM
• Reduce power to 1200 RPM for five minutes as a cool down period.
• Reduce throttle to idle.
• Pull mixture to IDLE cutoff and shut down the engine.
Almost ready to go fly . . . .
• Open the cowling.
• Inspect engine for leaks and make necessary adjustments.
• Check the installation of everything.
• Remove oil filter and inspect element or remove oil pressure screen and check for contamination.
• If no contamination is evident, the aircraft is ready for flight check.
I usually change the oil at this time. New filter, too.
Let the engine cool for 30 minutes.